1. Field of the Invention
The invention relates to a serpentine delay line structure, and more particularly to a serpentine delay line structure that includes plural winding serpentine delay line pairs mounted on the dielectric layer.
2. Description of the Prior Art
As communication technology prospers, various high-frequency electronic products appear and become the mainstream products in the marketplace. Also, the transmission speed of digital signals has increased dramatically. However, some communication problems for this high-frequency high-speed electronic industry, such as electromagnetic interference (EMI), electromagnetic compatibility (EMC), signal integrity (SI), power integrity (PI), and so on, are raised due to the increase in the transmission speed, and these problems affect the signal quality and integrity of the related circuits.
In addition, in a high-frequency system, the conventional single-ended signal wire can no longer meet the system's requirements, and thus, cannot ensure proper signal integrity. Therefore, for a modern high-frequency high-speed digital system, a method of applying differential signal line pairs to process the signal transmission is usually introduced to overcome the problems in common-mode noise and noise interference. Currently, various mainstream specifications for this method, including HDMI (High Definition Multimedia Interface 1.4/5 Gb/s), SATA (Serial Advanced Technology Attachment), USB3.0, PCI Express, Thunderbolt™, and so on, are all the application of the differential mode transmission. Nevertheless, if the differential signal line pair is not properly arranged, timing of the received signal would be unsynchronized, and thus the common-mode noise would be induced.
For example, refer to FIG. 1 for a conventional structure of a differential serpentine delay line. The serpentine delay line is usually seen on the printed circuit board for the aforesaid high-frequency high-speed products. As shown, the differential serpentine delay line PA1 consists two serpentine delay lines PA11 and PA12, in which the serpentine delay lines PA11 and PA12 are repeatedly bent on the substrate PA100.
However, since the travel paths for these two serpentine delay lines would differ, due to the winding, the timing for receiving the signals transmitted through these two individual serpentine delay lines would show a time lag, and thus, a common-mode noise would be induced. Obviously, the structuring of the conventional serpentine delay line, as shown in FIG. 1, does need further improvement.